Select the Expression That Completes the Formula Below $( x y ) ^ { k }$

Multiple Choice

Select the expression that completes the formula below. $( x y ) ^ { k }$

A) $x ^ { k } y ^ { k }$
B) $x ^ { m + k }$
C) $x ^ { m k }$
D) $\frac { x ^ { k } } { y ^ { k } }$
E) none of these